Device comprising two mutually adapted impedances for the purpose of power transmission

ABSTRACT

A device ( 1 ) for processing a signal (S) has firstly an antenna configuration ( 5 ) that is arranged to transmit a signal (S), that has at least one antenna-configuration terminal ( 6, 7 ) intended for connecting the antenna configuration ( 5 ) to a circuit ( 2 ), and that has an antenna-configuration impedance (ZA) at the antenna-configuration terminal ( 6, 7 ), and the circuit ( 2 ) further has at least one circuit terminal ( 3, 4 ) at which the circuit ( 2 ) has a circuit impedance (ZS) and at which the circuit ( 2 ) is connected to the antenna-configuration terminal ( 6, 7 ) for the purpose of power transmission between the antenna configuration ( 5 ) and the circuit ( 2 ) by using the signal (S), at least one of the two impedances (ZA, ZS) having, in respect of its reactance (YA, YS), a difference in reactance value (ΔY) from a nominal reactance value (Y NOM ) that is adapted for the transmission of power between the antenna configuration ( 5 ) and the circuit ( 2 ), and one of the two impedances (ZA, ZS) having a resistance (XA, XS) whose value (X) is greater than a nominal resistance value (X NOM ) that is adapted for the transmission of power between the antenna configuration ( 5 ) and the circuit ( 2 ) and is smaller than a maximum resistance value (X MAX ) that is a function of the difference in the reactance value (ΔY).

The invention relates to a device for processing a signal, which devicehas an antenna configuration, which antenna configuration is arranged totransmit a signal, the antenna configuration having at least oneantenna-configuration terminal that is intended for connecting theantenna configuration to a circuit and the antenna configuration havingan antenna-configuration impedance at the antenna-configurationterminal, and which device has the circuit, which circuit has at leastone circuit terminal at which the circuit has a circuit impedance and atwhich the circuit is connected to the antenna-configuration terminal forthe purpose of power transmission between the antenna configuration andthe circuit by using the signal, wherein at least one of the twoimpedances has, in respect of its reactance, a difference in reactancevalue from a nominal reactance value that is adapted for thetransmission of power between the antenna configuration and the circuit.

The invention further relates to an antenna configuration for a devicefor processing a signal, which antenna configuration is arranged totransmit a signal and which antenna configuration has at least oneantenna-configuration terminal that is intended for connection to acircuit of the device, the circuit having at least one circuit terminalat which the circuit has a circuit impedance and at which the circuit isconnectable to the antenna-configuration terminal by using the signalfor the purpose of power transmission between the antenna configurationand the circuit, and which antenna configuration has anantenna-configuration impedance at the antenna-configuration terminal,wherein at least one of the two impedances has, in respect of itsreactance, a difference in reactance value from a nominal reactancevalue that is adapted for the transmission of power between the antennaconfiguration and the circuit.

The invention further relates to a circuit for a device for processing asignal, which circuit has at least one circuit terminal at which thecircuit has a circuit impedance and at which the circuit is connectableto an antenna-configuration terminal for the purpose of powertransmission between an antenna configuration and the circuit by usingthe signal, which antenna configuration is arranged for the transmissionof the signal, which antenna configuration has at least oneantenna-configuration terminal that is intended for connecting theantenna configuration to the circuit, and which antenna configurationhas an antenna-configuration impedance at the antenna-configurationterminal, wherein at least one of the two impedances has, in respect ofits reactance, a difference in reactance value from a nominal reactancevalue that is adapted for the transmission of power between the antennaconfiguration and the circuit.

A device of the kind specified in the first paragraph, an antennaconfiguration of the kind specified in the second paragraph and acircuit of the kind specified in the third paragraph are known frompatent WO 00/67373.

The known device that has the known antenna configuration and the knowncircuit is a data carrier that is arranged for non-contactingcommunication with a communication arrangement. In the case of the knowndata carrier, a signal that is of a carrier frequency and that isemitted by the communication arrangement can be received by means of theantenna configuration and transmitted to the circuit. By using thesignal transmitted to it, the circuit is arranged to generate a supplyvoltage for its own operation, the value of the supply voltage that canbe generated being dependent on the distance at the time between thedata carrier and the communication arrangement and showing an increaseas the distance becomes smaller. The value of the supply voltage, andhence too the distance between the data carrier and the communicationarrangement that can be used for the operation of the data carrier, isalso affected by the electrical power that can be transmitted at thetime from the antenna configuration to the circuit. In the case of theknown data carrier, provision is therefore made, for the purpose ofoptimizing the power transmission, for an antenna impedance of theantenna configuration and a circuit impedance of the circuit to beadapted or matched, respectively, to one another, the value of theantenna-configuration impedance and the value of the circuit impedance,at a carrier frequency, being selected to have a complex conjugaterelationship to one another so that the reactances of the two impedancesare of a nominal reactance and the resistances of the two impedances areof a nominal resistance.

In the known data carrier, there is the problem that, despite theadaption of the two impedances to one another that supposedly benefitsthe transmission of power between the antenna configuration and thecircuit, at least one of the two impedances will in fact have, inrespect of its reactance, a difference in the value of its reactancefrom a nominal reactance value that is adapted to the transmission ofpower between the antenna configuration and the circuit. Even with arelatively small difference of only a few percent of the nominalreactance value, up to 40% of the distance that could be used if thereactance were of its nominal value can no longer be used, because thedifference in the reactance value causes a reflection when power istransmitted from the antenna configuration to the circuit, which meansthat the electrical power available in the circuit for generating thesupply voltage is reduced by the power that is reflected. A differencein reactance value of this kind may be caused in the antennaconfiguration for production-related reasons as a result of productiontolerances or of the connecting of the antenna configuration to thecircuit, or for use-related reasons as a result of environmental factorsor a change of carrier frequency. A difference in reactance value ofthis kind may be caused in the circuit too, for production-relatedreasons as a result of production tolerances, or for use-related reasonsas a result of a change of carrier frequency.

It is an object of the invention to overcome the problems stated abovein a device of the kind specified in the first paragraph, an antennaconfiguration of the kind specified in the second paragraph and acircuit of the kind specified in the third paragraph and to provide animproved device and an improved antenna configuration.

To achieve the object stated above, provision is made in a device of thekind specified in the first paragraph for one of the two impedances tohave a resistance whose value is greater than a nominal resistance valuethat is adapted from the transmission of power between the antennaconfiguration and the circuit and smaller than a maximum resistancevalue that is a function of the difference in the reactance value.

To achieve the object stated above, provision is made in an antennaconfiguration of the kind specified in the second paragraph for theimpedance of the antenna configuration to have a resistance whose valueis greater than a nominal value that is adapted from the transmission ofpower between the antenna configuration and the circuit and smaller thana maximum value that is dependent on the difference in the reactancevalue.

To achieve the object stated above, provision is made in a circuit ofthe kind specified in the third paragraph for the impedance of thecircuit to have a resistance whose value is greater than a nominal valuethat is adapted from the transmission of power between the antennaconfiguration and the circuit and smaller than a maximum value that isdependent on the difference in the reactance value.

The making of the provisions according to the invention gives theadvantage that, despite the difference in the reactance value, betterpower transmission is obtained when transmitting power between theantenna configuration and the circuit than would be the case if thenominal value of resistance were provided, the reason being that themaking of the provisions according to the invention allows a lower levelof reflection of the power to be achieved. Due to the improved powertransmission between the circuit and the antenna configuration, theadvantage is also obtained that the distance that can be used forcommunication between the device containing the circuit and the antennaconfiguration and a communication arrangement is increased as a functionof the improved transmission of power.

In the solutions according to the invention, it has also provedadvantageous if the features detailed in claim 2, claim 7 and claim 11are provided in the respective cases. This gives the advantage that itis possible for a range of resistance values in which the advantages ofthe invention are obtained to be defined in an analytically precisemanner without the use of complicated and costly measuring systems.

In the solutions according to the invention, it has also provedadvantageous if the features detailed in claim 3, claim 8 and claim 12are provided in the respective cases. This gives the advantage that,despite the existence of what is, in the conventional sense, an obviousmisadaption between the two impedances, optimized power transmissionbetween the antenna configuration and the circuit is obtained thatallows for the misadaption that exists in the given case.

In the solutions according to the invention, it has also provedadvantageous if the features detailed in claim 4, claim 9 and claim 13are provided in the respective cases. This gives the advantage that theadvantages of the invention are obtained particularly in the case of animpedance that has a high quality factor.

In one solution according to the invention, it has also provedadvantageous if the features detailed in claim 5 are provided. Thisgives the advantage that it is possible for an antenna configurationthat may have a high resistance value, as is preferred by antennamanufacturers, to be produced, and yet for there to be improved powertransmission, i.e. a gain in respect of the power transmission betweenthe antenna configuration and the circuit, without there also being adifference in the resistance value from the adapted resistance value aswell as the difference in the reactance value from the adapted nominalreactance value.

These and other aspects of the invention are apparent from and will beelucidated with reference to the embodiment described hereinafter, towhich however the invention is not limited.

In the drawings:

FIG. 1 is a block circuit diagram that shows, diagrammatically, a deviceaccording to the invention according to one embodiment of the invention.

FIG. 2 is a graph that shows, diagrammatically, a family of curves forthe ranges obtainable in communication between the device of FIG. 1 anda communication arrangement as a function of an antenna-configurationimpedance of an antenna configuration belonging to the device.

FIG. 3 shows, in a similar way to FIG. 2, the curve for the rangeobtainable for a given difference in reactance value shown by theantenna-configuration impedance, as a function of the resistance valueof a resistance of the antenna-configuration impedance.

Shown in FIG. 1 is a device 1 for processing a signal S, which device 1is formed by a data carrier 1 arranged for non-contacting communication,which data carrier 1 may take the form of a transponder, or anelectronic ticket, or a smart label or a chip card.

The signal S is implemented with the help of a carrier signal that is ofa carrier frequency and that is intended for the communication ofinformation between a communication arrangement (not shown in FIG. 1)and the data carrier 1, the carrier signal for communicating informationbeing amplitude-modulated as a function of the said information in thepresent case. It should however be mentioned at this point thatprovision may be made for any other kind of modulation, such amodulation in respect of phase or frequency for example. The signal S,which can be radiated from the communication arrangement at a definedpower, is also intended to supply the data carrier 1 with electricalpower. Hence the distance between the data carrier and the communicationarrangement that can be used for communication purposes is dependent onthe power that can be made available with the help of the signal S,which decreases with increasing distance, and on the power that the datacarrier is able to draw for its own operation.

The data carrier 1 has an electrical circuit 2 that is arranged forprocessing the signal S and that has for this purpose—as is sufficientlyfamiliar to the person skilled in the art—at least one section forprocessing analog signals (not shown in FIG. 1) and at least one sectionfor processing digital signals (not shown in FIG. 1), an a.c. equivalentcircuit diagram being shown in FIG. 1 to represent the a.c. electricalproperties of the at least two circuit sections. The a.c. equivalentcircuit diagram has a circuit resistance XS and a circuit reactance YS,the circuit resistance XS having a resistance value of 11.5 ohm and thecircuit reactance having a reactance value of −285 ohm. The circuitresistance XS and the circuit reactance YS form a circuit impedance ZS.The circuit 2 further has a first circuit terminal 3 and a secondcircuit terminal 4 at which the circuit 2 has the circuit impedance ZS.The circuit 2 is produced in the form of an integrated circuit in thepresent case, which means that, once the circuit has been manufactured,the value of its impedance ZS, which is set essentially by theparticular manufacturing process and the tolerances to which the processis subject, is virtually invariable.

The data carrier 1 further has an antenna configuration 5 that isarranged to transmit the signal S arising at it and that is produced inthe form of a dipole antenna in the present case. It should be mentionedat this point that some other type of antenna, such as a quadrupole or amonopole antenna for example, may also be provided. The antennaconfiguration 5 has a first antenna-configuration terminal 6 that isintended for connection to the first circuit terminal 3. The antennaconfiguration 5 also has a second antenna-configuration terminal 7 thatis intended for connection to the second circuit terminal 4. What isshown for the antenna configuration 5 in FIG. 1 is an a.c. antennaequivalent circuit diagram that represents the antenna configuration 5,or rather its a.c. electrical properties, in a.c. terms. The a.c.antenna equivalent circuit diagram has an antenna resistance XA and anantenna reactance YA. The antenna resistance XA and the antennareactance YA form an antenna impedance ZA. The antenna configuration 5has the antenna-configuration impedance ZA at the antenna-configurationterminals 6 and 7. The values concerned are, in accordance with theinvention, selectable, as will be described in detail below.

For the purpose of power transmission, and for the purpose ofinformation transmission, between the antenna configuration 5 and thecircuit 2, the first circuit terminal 3 and the firstantenna-configuration terminal 6, and the second circuit terminal 4 andthe second antenna-configuration terminal 7 are connected together, itbeing possible for the electrical power required for generating a supplyvoltage for the circuit 2 to be transmitted from the antennaconfiguration 5 to the circuit 2 by using the signal S that arises atthe antenna configuration 5.

The power that can be transmitted to the circuit 2 is dependent on thepower contained in the signal S that is received, i.e. mainly on thepower transmitted by the communication arrangement and/or the distancethat there is at the time between the communication arrangement and thedata carrier 1 and/or the orientation or attitude of the data carrier 1in space at the time. These dependences may be termed external inrelation to the data carrier 1 and do not concern the invention, sonothing further will be said about them in what follows.

The power that can be transmitted to the circuit 2 is also dependent onthe antenna-configuration impedance ZA or, to be more exact, on thequality of the adaption of the antenna-configuration impedance ZA to thecircuit impedance ZS. In relation to the data carrier 1, this dependenceis an internal dependence that does concern the invention and that willbe elucidated below by reference to FIG. 2.

Shown in FIG. 2 is a graph 8 in which the value X of the antennaresistance XA is shown along the X axis over a range between zero andeighty ohms and the value Y of the antenna reactance YA is shown alongthe Y axis over a range between two hundred and twenty-eight and threehundred and forty-two ohms. For each pair of values X and Y, thereflection coefficient Γ, which gives the proportion of reflected powerthat exists, as a function of the misadaption between the two impedancesZA and ZS, when power is transmitted between the antenna configuration 5and the circuit 2, can be calculated in conventional fashion from theformula given below.

$\Gamma = \frac{{ZS} - {ZA}^{*}}{{ZS} - {ZA}}$

Here, ZA* is the conjugate complex antenna-configuration impedance forthe antenna impedance ZA. For the transmission of power from the antennaconfiguration 5 to the circuit 2, this is dependent on the function(1−|Γ|²), which means that, if the value of the antenna impedance ZA is(11.5+i285) ohms, one hundred percent of the power can be transmittedfrom the antenna configuration 5 to the circuit 2 without any powerbeing reflected, which in turn means that, for a given transmittedpower, the maximum distance between a communication arrangement and thedata carrier 1 can be used for the purpose of communication in thisevent. Hence, when this is the case, the antenna resistance XA has anominal resistance value X_(NOM) of 11.5 ohm and the antenna reactanceYA has a nominal reactance value Y_(NOM) of 285 ohm. This ideal case isidentified in graph 8 by reference numeral 9.

Also shown in graph 8 are families of curves, of which one curve,standing for a plurality of curves, is identified by reference letter C.The parameter for the family of curves is the absolute value of thereflection coefficient |Γ|, with each curve representing, for a constantvalue of |Γ|, a constant distance between a communication arrangementand the data carrier 1 that can be used, as a maximum, forcommunication. Each curve is a function of the function √{square rootover (1−|Γ|²)} and is substantially in the form of an ellipse. In thecase of curve C, the maximum distance that can be used, which is afunction of the square root of the transmissible power, is 61.9% as apercentage of the distance that would be possible if theantenna-configuration impedance ZA were that that existed at point 9.The curves making up the family of curves therefore representdistance-specifying lines giving the maximum distances that can be usedfor communication.

When being manufactured, the antenna configuration 5 shown in FIG. 1 issubject to a tolerance on its antenna reactance, a mean difference inreactance ΔY of the order of approximately ±10% from the nominalreactance value of 285 ohm that is adapted for power transmissionbetween the antenna configuration 5 and the circuit 2 having been foundin random-sampling measurements actually made on a large number ofcompleted antenna configurations. This difference in reactance value ΔYfrom the nominal reactance value Y_(NOM) of 285 ohm is shown along the Yaxis in graph 8 by arrows 10 and 11. Hence, at the nominal resistancevalue X_(NOM) of 11.5 ohm, it would be possible to use only 63.5% of thedistance as compared with the adapted case. This unfavorable operatingpoint exists at a point 12 in graph 8.

To allow for the difference in reactance value ΔY, the antenna impedanceZA advantageously has an antenna resistance XA whose value is higherthat the nominal resistance value X_(NOM) that is adapted for thetransmission of power between the antenna configuration 5 and thecircuit 2 and is lower than a maximum resistance value X_(MAX) that is afunction of the difference in reactance value ΔY. Due to the facts thatthe ellipse that passes through point 12, which ellipse is not shown inFIG. 2 however, has a first axis of symmetry that extends parallel tothe X axis and passes through point 9, and that this ellipse has asecond axis of symmetry that extends parallel to the Y axis and issituated to the right of point 12, the maximum resistance value W_(MAX)is situated to the right of the nominal resistance value X_(NOM) and isapproximately 79.7 ohm in the present case. The functional dependencethat the maximum resistance value X_(MAX) shows on the difference inreactance value ΔY is given by the following formula:

${X_{MAX}({\Delta Y})} = {\frac{{\Delta Y}^{2}}{X_{NOM}} + X_{NOM}}$

The formula or function for the maximum resistance value X_(MAX) is theresult of the geometrical fact that the first dotted-and-dashed line 13that originates from point 12 and runs parallel to the X axis in graph 8intersects the ellipse passing through point 12 at a point 14. Theconditions in respect of power transmission that exist at the operatingpoint identified by point 14 are identical to those that exist at theoperating point identified by point 12. Because of the circumstancesrelating to symmetry affecting the ellipse that were explained above,there are two other points 15 and 16 in graph 8 to which what has justbeen said with regard to power transmission also applies. These twopoints 15 and 16 lie on a second dotted-and-dashed line 17 runningparallel to the X axis. Along line 13, there are ellipses intersectedbetween points 12 and 14 that indicate a distance that can be used forcommunication that is greater than is the case at points 12 and 14. Thesame is true of line 17.

The making of the provisions according to the invention therefore givesthe advantage that, with the given difference in reactance value ΔY, ifa resistance value X of between 11.5 ohm and 79.7 ohm is provided forthe antenna resistance XA, the power transmission that is obtainedbetween the antenna configuration 5 and the circuit 2 will be betterthan would be the case if the resistance value provided were the nominalone of 11.5 ohm. Consequently, the distance that can be used forcommunication purposes between the data carrier 1 and a communicationstation may also be a longer one than would be the case if theresistance value provided were the nominal X_(NOM).

To allow this advantage to be elucidated in detail, reference will bemade below to a second graph 18 that is shown in FIG. 3, in which thedistance D between a communication station and the data carrier 1 isshown as a function of the value X of the antenna resistance XA. A firstfunction F1 that is plotted in graph 18 defines the maximum availabledistance as a function of the antenna resistance XA, when the antennareactance YA is of the nominal reactance value Y_(NOM). The firstfunction F1 should be seen in this case as representing a sectionthrough the graph 8 in FIG. 2 on a line C1. A second function F2 and athird function F3 that are plotted in graph 18 each define the maximumavailable distance as a function of the antenna resistance XA, when theantenna reactance YA is of the differing reactance value ΔY, these twofunctions F2 and F3 coinciding in this case. The second function F2should be seen as representing a section through graph 8 on a line C2and the third function as representing a section through graph 8 on aline C3. It can be seen from graph 18 that along the dotted-and-dashedlines 13 and 17 shown in graph 8 there is a gain in usable distancebetween points 12 and 14 and points 15 and 16 respectively as comparedwith the usable distance that exists at points 12, 14, 15 or 16.

The functions F2 and F3 are at a maximum of approximately 30.3 ohm atpoints that are identified by reference numerals 01 and 02 respectively,this maximum being defined as an optimum resistance value X_(OPT).Provision is made in accordance with the invention for the antennaresistance XA of the antenna configuration 5 to be of the optimumresistance value X_(OPT), in which case the optimum resistance valueX_(OPT) can be calculated analytically from the formula given below:X _(OPT)(ΔY)=√{square root over (X _(NOM) ² +ΔY ²)}

The maxima of functions F2 and F3 that are identified by referencenumerals 01 and 02 respectively are shown in graph 8 as, respectively,the intersection of line 13 with a line 19 that runs parallel to the Yaxis and intersects the X axis at the optimum resistance value X_(OPT),and the intersection of line 17 with line 19. At these intersections,lines 13 and 17 form tangents to an ellipse that represents the maximumusable distance D(X_(OPT),ΔY)=74.2% between a communication station andthe data carrier 1 that exists, as a percentage ofD(X_(NOM),Y_(NOM))=100% in the ideally adapted case, when there is themisadaption ΔY. This should be considered in relation to the maximumusable distance of D(X_(NOM),ΔY)=63.5% or D(X_(MAX),ΔY)=63.5% that wouldbe obtained in the case of the nominal resistance value X_(NOM) or themaximum resistance value X_(MAX). The loss of maximum usable distance atthe operating point that is preferred in accordance with the inventionis therefore merely (100−74.2)%=25.8% as compared with(100−63.5)%=36.5%, which gives a gain in respect of distance ofcommunication of (74.2−63.5)%=10.7%.

This gives the advantage that optimum conditions with respect to thetransmission of power between the antenna configuration 5 and thecircuit 2 can virtually always be produced, in a repeatable and reliablemanner, for virtually any desired difference in reactance value ΔY. Theadvantages of the invention exist in particular when the quality of theantenna impedance ZA, which is given by the formula Q=YA/XA, is greaterthan 2, because otherwise the shape of the ellipses is such that theeffect that boosts the transmission of power comes into play to only asmall extent or hardly at all.

Even though the situation relating to the two impedances ZA and ZS thatwas described in the case of the embodiment discussed above was suchthat only the antenna reactance YA had a mean difference in reactancevalue ΔY and the circuit impedance ZS was of a value that waspractically invariable after the circuit was manufactured, which wasdone to make the invention easier to describe, it should be expresslymentioned at this point that the circuit impedance ZS too may be subjectto a tolerance in respect of the reactance value Y of the circuitreactance YS due to the process by which the circuit is manufactured,which means that the circuit reactance YS too may have a mean differencein reactance value ΔY of a certain size. The differences in reactancevalue ΔY of the circuit reactance YS and the antenna reactance YA may beindependent of one another and may both be present simultaneously. Thisis the situation that exists when, for example, due to statutorystipulations or technical factors, provision has to be made from astepped change in frequency, as a result of which there is a change inthe circuit reactance YA and the antenna reactance XA due to theirdependence on frequency. A difference in reactance value ΔY of this kindmay also be caused by a frequency error on the part of a transmittingmeans for generating the signal S. Something else that should bementioned at this point is that a difference in reactance value ΔY mayalso be caused by the process of manufacturing the device and inparticular by the connection of the antenna configuration 5 to thecircuit 2 or by the effect of environmental conditions on the antennaconfiguration 5. However, it has proved advantageous in all such casesif the steps according to the invention are taken, because this benefitsthe transmission of power between the antenna configuration 5 and thecircuit 2 even when there is an obvious misadaption of the tworeactances YS and YA to one another.

Even though what was taken as a basis in the case of the embodimentdiscussed above was the transmission of power for the purpose ofgenerating a supply voltage for the circuit 2 of the data carrier 1, itshould be mentioned that the making of the provisions according to theinvention promotes not only an improved transmission of power but alsoan improved transmission of information between the antennaconfiguration 5 and the circuit 2 because, due to a reduction in theabsolute value of the reflection coefficient |Γ|, there is also animprovement in the signal-to-noise ratio, which ratio has an essentialrole in the processing of the information.

It should also be mentioned that—as is the case in, for example, adevice 1 that forms a radio set or a mobile telephone—the circuit 2 mayalso be so designed as to actively generate a signal S and this signal Smay be emittable from the circuit 2 to the antenna configuration 5, fromwhere the signal S is to be radiated at a defined transmitted power,thus enabling the advantages of the invention that are described aboveto come into play in the transmission of power and/or information fromthe circuit 2 to the antenna configuration 5.

It should also be expressly mentioned at this point that the featuresaccording to the invention relating to resistance, or rather its value,may be provided in the case of both the antenna configuration 5 and thecircuit 2, regardless of whether the difference in reactance value ΔY ispresent in the antenna configuration 5 or in the circuit 2.

It should further be mentioned that the antenna configuration 5 may alsohave more than a single antenna.

1. A device for processing a signal, the device comprising: an antennaconfiguration; and a circuit; wherein the antenna configuration isarranged to transmit a signal, the antenna configuration having at leastone antenna-configuration terminal that is intended for connecting theantenna configuration to the circuit and the antenna configurationhaving an antenna-configuration impedance (ZA) at theantenna-configuration terminal; wherein the circuit has at least onecircuit terminal at which the circuit has a circuit impedance (ZS) andat which the circuit is connected to the antenna-configuration terminalfor the purpose of power transmission between the antenna configurationand the circuit by using the signal, wherein at least one of the twoimpedances (ZA, ZS) has, in respect of its reactance(YA, YS), adifference in reactance value (ΔY) from a nominal reactance value(Y_(NOM)) that is adapted for the transmission of power between theantenna configuration and the circuit, characterized in that one of thetwo impedances (ZA, ZS) has a resistance (XA, XS) whose value is greaterthan a nominal resistance value (X_(NOM)) that is adapted from thetransmission of power between the antenna configuration and the circuitand is smaller than a maximum resistance value (X_(MAX)) that is afunction of the difference in the reactance value (ΔY).
 2. A device asclaimed in claim 1, characterized in that the functional dependence thatthe maximum resistance value shows on the difference in reactance valueis given by the formula:X _(MAX)(ΔY)=(ΔY ² /X _(NOM))+X _(NOM) where ΔY is the difference inreactance value and X_(NOM) is the nominal resistance value.
 3. A deviceas claimed in claim 1, characterized in that the resistance whoseresistance value is greater than the nominal resistance value that isadapted for the transmission of power between the antenna configurationand the circuit and is smaller than the maximum resistance value that isa function of the difference in reactance value is an optimum resistancevalue given by the formula:X _(OPT)(ΔY)√{square root over (X _(NOM) ² +ΔY ²)} where ΔY is thedifference in reactance value and X_(NOM) is the nominal resistancevalue.
 4. A device as claimed in claim 1, characterized in that thequality of the two impedances has a value that is greater than two.
 5. Adevice as claimed in claim 1, characterized in that theantenna-configuration impedance has a resistance whose value is greaterthan the nominal resistance value that is adapted for the transmissionof power between the antenna configuration and the circuit and issmaller than the maximum resistance value that is a function of thedifference in reactance value.
 6. An antenna configuration for a devicefor processing a signal, which antenna configuration is arranged totransmit a signal,the antenna configuration comprising: at least oneantenna-congiuration terminal that is intended for connection to acircuit of the device, the circuit having at least one circuit terminalat which the circuit has a circuit impedance (ZS) and at which thecircuit is connectable to the antenna-configuration terminal for thepurpose of power transmission between the antenna configuration and thecircuit by using the signal, wherein the antenna configuration has anantenna-configuration impedance (ZA) at the antenna-configurationterminal, wherein at least one of the two impedances (ZA, ZS) has, inrespect of its reactance (YA, YS), a difference in reactance value (ΔY)from a nominal reactance value (Y_(NOM)) that is adapted for thetransmission of power between the antenna configuration and the circuit,characterized in that the impedance (ZA) of the antenna configurationhas a resistance (XA) whose value is greater than a nominal resistancevalue (X_(NOM)) that is adapted from the transmission of power betweenthe antenna configuration and the circuit and is smaller than a maximumresistance value (X_(MAX))that is a function of the difference inreactance values(ΔY).
 7. An antenna configuration as claimed in claim 6,characterized in that the functional dependence that the maximumresistance value shows on the difference in reactance value is given bythe formula:X _(MAX)(ΔY)=(ΔY ₂ /X _(NOM) where ΔY is the difference in reactancevalue and X_(NOM) is the nominal resistance value.
 8. An antennaconfiguration as claimed in claim 6, characterized in that theresistance whose resistance value is greater than the nominal resistancevalue that is adapted for the transmission of power between the antennaconfiguration and the circuit and is smaller than the maximum resistancevalue that is a function of the difference in reactance value, is anoptimum resistance value given by the formula:X _(OPT)(ΔY)√{square root over (X _(NOM) ² +ΔY ²)} where ΔY is thedifference in reactance value and X_(NOM) is the nominal resistancevalue.
 9. An antenna configuration as claimed in claim 6, characterizedin that the quality of the antenna-configuration impedance has a valuethat is greater than two.
 10. A circuit for a device for processing asignal, the circuit comprising: at least one circuit terminal at whichthe circuit has a circuit impedance (ZS) and at which the circuit isconnectable to an antenna-configuration terminal for the purpose ofpower transmission between an antenna configuration and the circuit byusing the signal, which antenna configuration is arranged for thetransmission of the signal which antenna configuration has at least oneantenna-configuration terminal that is intended for connecting theantenna configuration to the circuit, and which antenna configurationhas an antenna-configuration impedance (ZA) at the antenna-configurationterminal, wherein at least one of the two impedances (ZA, ZS) has, inrespect of its reactance (YA, YZ), a difference in reactance value (ΔY)from a nominal reactance value (Y_(NOM)) that is adapted for thetransmission of power between the antenna configurations and thecircuit, characterized in that the impedance of the circuit (ZS) has aresistance (XS) whose value is greater than a nominal resistance value(X_(NOM)) that is adapted from the transmission of power between theantenna configuration and the circuit and is smaller than a maximumresistance value (X_(MAX)) that is a function of the difference in thereactance value (ΔY).
 11. A circuit as claimed in claim 10,characterizedin that the functional dependence that the maximum resistance valueshows on the difference in reactance value is given by the formula:X _(MAX)(ΔY)=(ΔY ² /X _(NOM))+X_(NOM) where ΔY is the difference inreactance value and X_(NOM) is the nominal resistance value.
 12. Acircuit as claimed in claim 10, characterized in that the resistancewhose resistance value is greater than the nominal resistance value thatis adapted for the transmission of power between the antennaconfiguration and the circuit and is smaller than the maximum resistancevalue that is a function of the difference in reactance value, is anoptimum resistance value given by the formula:X _(OPT)(ΔY)√{square root over (X _(NOM) ² +ΔY ²)} where ΔY is thedifference in reactance value and X_(NOM) is the nominal resistancevalue.
 13. A circuit as claimed in claim 10, characterized in that thequality of the circuit impedance has a value that is greater than two.